The present invention relates to gas turbine engines, and more particularly, to bearing compartments in gas turbine engines.
The rotating shafts and other rotating turbomachinery of gas turbine engines are supported from a non-rotating structure by arrays of anti-friction bearings. In many engines, the anti-friction bearings are enclosed in bearing compartments that are in part bounded by an outer wall circumscribing the engine shafts. A lubricant such as oil is supplied to the bearing compartments to lubricate and cool the anti-friction bearings during operation of the gas turbine engine. The bearing compartments are sealed to protect the anti-friction bearings from debris introduced into the gas turbine engine and to restrict the lubricant from entering undesired areas of the engine. To accomplish bearing compartment sealing, carbon seals are commonly used. Additionally, a high pressure buffer air (also called pressurization air) flow is commonly supplied to the bearing compartments through the seals from sources within the gas turbine engine such as the compressor section. The buffer air aids in restricting the lubricant to bearing compartments.
The high pressure buffer air flow is also used for other purposes including providing a nose cap of an engine fan with anti-icing heat. To create sufficient buffer air flow for all purposes including anti-icing and sealing, an additional seal must be positioned upstream of each bearing compartment seal to create a sufficient back pressure to induce flow. Unfortunately, the upstream seal has been known to generate debris that can be introduced into the bearing compartment seal causing its premature failure.